import matplotlib.pyplot as plt
import numpy as np

from matplotlib.patches import Rectangle
from itertools import chain

ax, fig = plt.subplots(1,4)

xs = np.linspace(0.0, 1.5, 1e4)
ys = xs*xs

ax.set_figwidth(20)
ax.set_figheight(4)

epsilons = [0.8, 0.6, 0.4, 0.2]

for f, eps in zip(fig, epsilons):
    delta = eps/3
    
    f.plot(xs, ys)
    f.set_ylim((0,2))
    f.set_xlim((0,2))
    
    f.add_patch(Rectangle((1-delta,1-eps), 2*delta, 2*eps,
                          edgecolor="black", facecolor="#dddddd",
                          alpha=0.6, linestyle="solid", lw=1.5))
    
    xs_delta = xs[(xs > 1-delta) & (xs < 1+delta)]
    f.plot(xs_delta, xs_delta*xs_delta, color="green", lw=3)
    
    
    f.plot([1], [1], "o", color="black")

ax.savefig("Dependence of delta with epsilon in case of the continuous square function.svg", bbox_inches='tight', pad_inches=0.5)